1. Field of the Invention
The present invention relates to an illumination key for use in various mobile communication devices, such as cellular phones and automobile phones, and various terminal devices, such as electronic organizers and the like, to enable the keys thereof to be visible in nighttime and low light conditions. The present invention further relates to a method of manufacturing such illumination key.
2. Description of the Prior Art
In the prior art, this type of illumination key is constructed by forming a printed pattern layer, such as a character or the like, into the underside surface of a key top made of light-permeable resin and then fixing a silicon rubber key operating portion to the back side of the printed pattern layer by means of silicon rubber and an adhesive having good adhesive properties.
Further, in the case where a printed pattern layer, such as a character or the like, is formed in the surface of the key top, the etching of the character is carried out with a laser beam, and this makes such prior art illumination keys expensive to manufacture.
Furthermore, because prior art illumination keyes are not designated to allow for reduction in size and weight of the key unit when manufacturing thin keytops, it is not possible to meet the market needs for ultralight keytops.
Moreover, because the printed pattern (character) layer is formed in the underside surface of the light-permeable resin key top, the printed pattern (character) is difficult to see in the illumination key described above in the case where the upper surface of the key top has a curved shape.
Furthermore, because the printed pattern (character) is etched by means of a laser beam, it is not possible to prevent high costs when manufacturing such illumination keys.
Moreover, in the case where a printed pattern (characters) is formed on one side of a film which is placed over a plurality of light-permeable resin key tops and heat fused to the upper and side surfaces thereof, because the key tops are connected to each other via the film, misoperations can occur when the operation of one key top also operates a neighboring key top.
Further, when designing a lightweight keytop, it is difficult to adequately bond the keytop and the key operating portion.